The Giants show up at MetLifeSupport Stadium today teetering on the physical cliff, the winter of their discontent awaiting their fall.

Their Super Bowl defense could end by 4 p.m. Or it could end by 7:30 p.m. Or it could end by 11:45 p.m.

Or maybe they will remember how champs are supposed to respond, and maybe the Lions will beat the Bears on an Immaculate Reception, and maybe this time the Packers will win a game on a Fail Mary against the Vikings, and maybe Robert Griffin III will watch Pierre Garçon or Santana Moss catch some desperation heave in the fourth quarter pressed against his helmet to beat the Cowboys.

A win and a prayer at 1 p.m.

One more prayer at 4:25 p.m.

One last prayer at 8:30 p.m.

Shame on the Giants for finding themselves in this predicament, their backs against the wall, wondering if the blindfold and the cigarette are imminent.

A far more unforgivable shame, and one that would deserve dire offseason consequences for an organization obsessed with winning instead of publicity, would be losing to Michael Vick and Andy Reid if the Lions upset the Bears, the Packers beat the Vikings and the Redskins beat the Cowboys.

It is unbecoming of any champion in any sport to quit in his corner, and no matter what happens everywhere else, if the 2012 Giants cannot summon up enough pride, dignity and honor to take care of their business in front of their own fans — and anguished Sandy Hook survivors — against a rival they genuinely hate, they will be remembered as the football Roberto Duran, champions of No Mas.

The Giants should recognize waking up tomorrow morning in the playoffs with a chance to defend their title, as improbable as it seems, is more improbable than it is impossible.

The drama starts at 1, at MetLife-support Stadium and at Ford Field.

This is the Eagles’ Super Bowl, so the Giants cannot afford to keep one eye on them and the other on the scoreboard. Vick, auditioning for his next team, will try to torch a wounded secondary, and LeSean McCoy, in his second game back from a concussion, will try to torment Big Blue again. Eli Manning, who has stopped throwing touchdown passes at the worst possible time, will need to be elite, even with a hobbled Hakeem Nicks, and must find Victor Cruz early and often.

But all’s not lost Giants fans. The Lions hate the Bears, so this will amount to a Super Bowl of sorts for them, where Megatron Johnson needs 108 receiving yards to reach 2,000. These reeling Bears, who have all the pressure on them fighting for the playoffs, are hardly Monsters of the Midway. If Ndamukong Suh pancakes Jay Cutler to the ground the way he did in the first meeting, no one should be surprised. And expect Suh to be motivated by the fact Bears defensive tackle Henry Melton was voted to the Pro Bowl ahead of him.

Giants hearts begin racing should they leave MetLife-support Stadium with hope, and turn their eyes to the Metrodome, where the Packers crave the No. 2 seed while the Vikings fight for their playoff lives. Because that’s where their fate will rest, in the wondrous hands of Aaron Rodgers, who will try to jump out quickly and force Christian Ponder to play catchup. The Vikings will pound Adrian Peterson all day if they can, and the home crowd will try to will him past Eric Dickerson’s single-season record, but if you think he’ll be able to rush for 210 yards again this time with an abdominal strain, think again.

It is 7:30, and the Giants are still alive.

In one hour, as much as it appalls them, they will be glued to their televisions, singing “Hail to the Redskins.”

RGIII versus Tony Romo. Countless TV shots of Jerry Jones. Alfred Morris will try to gash a battered Rob Ryan defense, so Romo has less time to get the ball to Dez Bryant, a huge problem for DeAngelo Hall and Josh Wilson.

If the Bears and Vikings lose, the Redskins are in the playoffs as a wild card.

All or nothing for the Cowboys. All or nothing for the Giants.

It is Monday morning, and coach Tom Coughlin opens his team meeting by leading a chorus of “Hail to the Giants.”